This invention relates to color printing equipment and more particularly to equipment for applying a photosensitive emulsion to a backing sheet and simultaneously drying the emulsion.
In the printing industry, a proof of a color print is often required prior to setting up the printing press. In order to provide a proof, several photosensitive films, each comprising a color separation positive, are laminated together to produce the finished proof which is then examined prior to setting up the printing press. Typical colors are black, cyan, magenta and yellow, but one or more additional colored sheets may be required particularly if the customer needs to print a special or unusual color. To do this, a specially coated sheet may be required. The present invention is particularly well adapted to preparing photosensitive coated sheets used in proofing color printing.
To effectively apply such a coating and provide the required coating quality and uniformity i.e., to maintain the required coating thickness and to assure a smooth surface as well as to achieve the required hardness when the sheet is ready to be removed from the coater, the coating must be dried under controlled conditions. Such conditions are difficult or impossible to achieve with available equipment. The applied coating must be dry to the touch shortly after being coated and before the sheet is removed from the coater, usually less than five minutes from the time the coating is applied. In developing the present invention, it was discovered that it is advantageous to continuously and progressively dry the coating as the coating is being applied. It was discovered that doing so would stabilize the coating while maintaining a smooth surface so that the sheet can be handled almost immediately after the coating is applied.
Another shortcoming of previous equipment is that there has previously been no way to apply a coating in a given feed direction e.g., from left to right and subsequently dry the applied coating in a reverse direction from right to left. To make this possible it was necessary to find a way to spread the coating evenly in the first pass and then make a second pass without the coating applicator in place which, if present, would damage the applied coating as it was carried back across the coated material.
Another problem is caused by the coating material that clings to the coating applicator and must be removed before it has hardened. An additional deficiency of prior equipment is the lack of an easy way of washing the coating applicator once the coating has been applied.
In view of these and other deficiencies of the prior art it is one object of the invention to provide an improved emulsion coater for effectively applying and simultaneously drying a photosensitive photographic coating onto a backing sheet.
Another objective of the invention is to find a way to dry an emulsion coating material in an area that is just behind the leading edge of the freshly applied coating while it is being applied.
Yet another object in the invention is the provision of the improved coating apparatus for progressively coating a backing sheet in a given feed direction with a provision for automatically disconnecting and removing the coating applicator once the backing has been completely coated so that it can be picked up manually and washed.
Another object is to find a way of applying an emulsion progressively across a backing sheet and thereafter drying the applied coating without the requirement of an oven next to the coater for receiving the freshly coated sheet.
Yet another object of the present invention is to provide an improved coating applicator having a simple but effective provision for quickly and easily removing spilled coating material from the work surface.
These and other more detailed and specific objects of the present invention will be better understood by reference to the following figures and detailed description which illustrate by way of example but a few of the various forms of the invention within the scope of the appended claims.